The disclosed technology regards a chainsaw guard mountable on a chainsaw, the chainsaw guard forming a physical barrier that limits access to the chainsaw's saw cutter chain when the chainsaw guard is mounted on the powerhead housing. The chainsaw guard of the disclosed technology positions a retractable member relative to a bracket member in an extended position, partially sheathing the chainsaw saw cutter chain until a force greater than the spring force is applied to the distal end of the retractable member, translating the retractable member towards a retracted position; when the force is removed from the distal end of the retractable member, the retractable member moves back to the extended position by means of the spring force.
Chainsaw usage by relatively unskilled personnel has increased in recent years and as a result the number of chainsaw accidents has increased. Gasoline, electric and battery powered chainsaws have become increasingly popular for suburban dwellers having relatively little experience in their use. Exposed saw cutting chains are dangerous whether running or idle, and inexperienced users cutting brush or trimming the tops of trees or small limbs sometimes come in contact with the upper part of the cutting chain. Also, while cutting, the cutting chain can become wedged or lodged in a tree trunk or limb, which stops the cutting chain movement and causes it to react by “kicking-back” violently.
Kickback of a chainsaw is when the teeth on the chain catch on material (e.g., wood or metal) as they rotate around the tip of the blade. The teeth may have enough force to cause the blade to kick back violently toward the chainsaw operator, hence the term “kickback.” In some examples, kickback may occur when the nose of the blade of a chainsaw strikes another object such as a metal spike, when starting a bore cut improperly, and when the blade nose or tip of the chainsaw catches the bottom or side of a saw cut during reinsertion. Kickback is particularly dangerous because it is so violent and it occurs so rapidly that the chainsaw operator is challenged to avoid serious injury. The chainsaw reacts by kicking back violently in an upwardly rotating arc, and thus back toward the head, shoulders and chest of the operator, potentially causing serious injury.
Another potentially injurious problem with chainsaws involves cut-through, which occurs when the chainsaw blade passes through the wood and continues to swing downward towards the lower body of the operator. This loss of control may occur if the chainsaw operator is poorly trained or distracted. In one example, a chainsaw operator may saw through a log and be unprepared when the log is cut all the way through. Pressure on the chainsaw may cause the chainsaw to complete the cut and then torque towards an unprotected portion of the operator's body.
Dropping an active chainsaw may also lead to significant injury. These kinds of accidents may occur if the chainsaw is being used in a tree or by an inattentive operator who allows the chainsaw to slip from the operator's grip. Further, because of the sharp edges of cutter chains, chainsaws may even cause injuries to individuals carrying or handling the chainsaws, and their sharp edges may be damaged by unintended contact with objects.
In the prior art a number of devices are known which either surround or cover the guide bar on a chainsaw to prevent contact between the saw chain and the user in the event of chainsaw kickback or cut-through. In order for the saw to continue to have full utility, guards must allow the saw to pass through the material being cut, without interference. To this end, a variety of springs, levers and guard configurations have been proposed. While the devices may be useful, they do tend to limit the utility of the chainsaw because of the complexity of the mounting mechanism and of the guard devices, or they provide protection either for kickback or cut-through, but not for both.
Patents that disclose a guard for a chainsaw include U.S. Pat. Nos. 2,638,944; 4,143,460; 4,447,953; 4,841,641; 4,945,641; 4,991,297; and, 5,179,785.
One way previously proposed to minimize the risk of such injuries and damage was to place a chainsaw in a sealed portable case or similar container. However, the substantial weight and volume of such cases rendered them unattractive to individuals using them, especially loggers, who frequently have to carry chainsaws on foot to working sites. Exemplary cases are described in Schurman U.S. Pat. No. 4,369,575 granted Jan. 25, 1983, Reynolds U.S. Pat. No. 5,119,937 granted Jun. 9, 1992, and Griffin U.S. Design Pat. No. 359,849 granted Jul. 4, 1995.
Another way previously proposed to prevent such injuries was to provide a guard, sheath, or the like to limit access to the cutter chain. However, in many such proposed devices, the protection provided the individual was during sawing operation, not primarily protection during carrying or transporting the chainsaws. For example, many bar guards, sheaths, or the like were designed to prevent kickback when operating the chainsaw. Therefore, a portion of the cutter chain was always exposed when using such devices; the possibility of damage or injury during transportation was not prevented. An exemplary open guard is illustrated in Holzworth U.S. Pat. No. 4,193,193 granted Mar. 18, 1980. A similar such guard hingedly connected to the saw is described in Shivers U.S. Pat. No. 4,621,426 granted Nov. 11, 1986. The Shivers bar guard remains attached to the saw during the sawing operation while it is pivoted upwards away from the guard, interfering with the operator's view of the log or other workpiece.
Other such protective devices often required some modification of the chainsaw itself. By way of example, in Otoupalik U.S. Pat. No. 3,042,087 granted Jul. 3, 1962, a protective sheath was designed to be removably attached to the chainsaw by a pair of removable tension springs. The cutter chain was completely sealed when the sheath was attached. However, the primary objective of the described invention was to protect the cutter chain and guide bar from damage during transportation of the chainsaw. As a result, the combined chainsaw and guard remained hazardous to the person carrying the chainsaw with the sheath thereon. For example, since the tension springs were hooked onto the chainsaw handle bar, the springs often interfered with carrying the chainsaw. Further, when the sheath was attached, the tension springs were always in extension. Thus, it was quite possible that the person carrying the chainsaw with the sheath thereon might be injured by the tension spring if it were accidentally dislodged. Simply by using the Otoupalik device, the risk of at least some types of injury increased.
Woleslagle U.S. Pat. No. 2,683,944 granted May 19, 1953 discloses a telescoping sheath that provides blade protection during transport and a set of concentric telescoping spring loaded tubes to restore the telescoping sheath to its resting, protective position. The disclosed concentric telescoping spring loaded tubes must move freely and rapidly. To reduce friction, the cutting chain must be well lubricated, most desirably with a viscous oil that will cling to the chain. This feature is counter to that desired for the concentric telescoping spring-loaded tubes of Wolesage, that must move freely and rapidly. Specifically, so that the lubricant clings to the rapidly moving saw chain, a higher viscosity lubricant is desirable; for the concentric telescoping spring-loaded tubes a lubricant with low viscosity is appropriate. A design that functions with a single lubricant is needed.
Chainsaws are inherently dangerous implements for both experienced accidental and inexperienced operators. Even the briefest contact between the saw operator and a moving saw chain can cause serious and often permanent injury. Because of the potential for dangerous accidents, numerous devices have been developed and patented over the years to protect the chainsaw operator. Examples of prior art safety guards include devices which extend along one edge of the cutter bar and pivot out of the way, as shown in U.S. Pat. Nos. 3,384,136 and 4,060,894; pivoting covers that fully or partially sheath the cutter bar and pivot out of the way during use, as shown in U.S. Pat. Nos. 3,059,673 and 4,257,162; or a telescoping full saw enclosure which collapses out of the way of the cutter bar, as shown in U.S. Pat. No. 2,638,944. Many of these prior art devices are cumbersome to use, can become clogged with sawdust and wood chips, and may seriously interfere with the operator's view of the cutter bar when the saw is in use or protect only one edge of the saw. For these and other reasons, most chainsaw safety guard devices remain unpopular with saw owners and manufacturers.